The mechanical watch movement that we know today is the result of successive improvements over the last three centuries. The Swiss lever escapement is characterized by its robustness to shocks. That is to say that the state of the watch is little affected by a one-off shock.
However, the efficiency of such an escapement is not very good (around 30%). Moreover, the Swiss lever escapement does not permit the use of resonators with a high frequency or low amplitude.
Ways are therefore sought to use resonators having a high quality factor, a high frequency, and/or low amplitude, while increasing the efficiency of the escapement and without sacrificing its robustness to shocks.
Among the embodiments relating to the field of the invention, the following are known:
the tuning fork clock developed by Clifford;
the Resonique® movement developed by De Bethune®,
the Accutron® watch developed by Bulova®.
Each of these embodiments offers particular advantages, but these movements have the same drawback: they are not resistant to shocks. That is to say that, in the event of a shock, the hands rapidly gain time.
EP Patent Application 2889704A2 in the name of Nivarox-FAR SA discloses a timepiece escapement mechanism, comprising an escape wheel subjected to a rotational torque, having a moment of inertia lower than or equal to a nominal moment, about a first pivot axis, and a resonator integral with a regulating wheel set mounted to pivot about a second real or virtual pivot arbor/axis, said escape wheel comprising a plurality of actuators regularly spaced on its periphery and each arranged to cooperate directly with at least a first track of said regulating wheel set, characterized in that each said actuator includes first magnetic or electrostatic stopping means forming a barrier, and arranged to cooperate with said first track which is magnetically, or respectively electrically charged, or ferromagnetic, or respectively electrostatically conductive, to exert on said first track a torque having a moment greater than said nominal moment, and further characterized in that each said actuator also includes second stopping means arranged to form an end-of-travel stop, arranged to form an autonomous escapement mechanism with at least a first complementary stop surface comprised in said regulating wheel set.
WO Patent Application 2015/096979A2 in the name of The Swatch Group Research & Development Ltd discloses a timepiece escapement mechanism comprising a stop member between, on the one hand, a resonator, and on the other hand, two escape wheel sets each subjected to a torque, characterized in that each said escape wheel set comprises at least one magnetized or ferromagnetic, or respectively, electrically charged or electrostatically conductive track with a period of travel over which its magnetic, or respectively, electrostatic characteristics are repeated, said stop member including at least one magnetized or ferromagnetic, or respectively, electrically charged or electrostatically conductive pole piece, said pole piece being mobile in a transverse direction relative to the direction of travel of at least one element on a surface of said track, and at least said pole piece or said track creating a magnetic or electrostatic field in an air-gap between said at least one pole piece and said at least one surface, and further characterized in that said pole piece confronts a magnetic or electrostatic field barrier on said track just before each transverse motion of said stop member controlled by the periodic action of said resonator, and characterized in that said first escape wheel set subjected to a first torque and said second escape wheel set subjected to a second torque are each arranged to be capable of cooperating alternately with said stop member, and in that said first escape wheel set and said second escape wheel set pivot about distinct axes and are connected to each other by a direct kinematic connection.
U.S. Pat. No. 3,183,426A in the name of HAYDON ARTHUR describes an entirely magnetic escapement including a magnetic escape wheel, in which the energy varies continuously and progressively between minimum and maximum when the wheel turns through one half-period and then the energy returns to a minimum value over the following half-period. In other words, the magnetic force on the wheel varies progressively between a minimum (negative) and maximum (positive) value over an angular period.